Mechanical support of an indirect contact lens by a surgical microscope during vitreoretinal surgery

ABSTRACT

An indirect contact lens is mechanically coupled to a surgical microscope during ophthalmic surgery, such as vitreoretinal surgery. The indirect contact lens rests on a cornea of an eye of a patient during the surgery but is supported by a surgical microscope attachment having multiple degrees of freedom to accommodate small movements of the eye while remaining aligned to an optical axis of the surgical microscope.

BACKGROUND Field of the Disclosure

The present disclosure relates to ophthalmic surgery, and morespecifically, to mechanical support of an indirect contact lens by asurgical microscope during vitreoretinal surgery.

Description of the Related Art

In ophthalmology, eye surgery, or ophthalmic surgery, is performed onthe eye and accessory visual structures. More specifically,vitreoretinal surgery encompasses various delicate procedures involvinginternal portions of the eye, such as the vitreous humor and the retina.Different vitreoretinal surgical procedures are used, sometimes withlasers, to improve visual sensory performance in the treatment of manyeye diseases, including epimacular membranes, diabetic retinopathy,vitreous hemorrhage, macular hole, detached retina, and complications ofcataract surgery, among others.

During vitreoretinal surgery, an ophthalmologist typically uses asurgical microscope to view the fundus through the cornea, whilesurgical instruments that penetrate the sclera may be introduced toperform any of a variety of different procedures. The surgicalmicroscope provides imaging and optionally illumination of the fundusduring vitreoretinal surgery. The patient typically lies supine underthe surgical microscope during vitreoretinal surgery and a speculum isused to keep the eye exposed. Depending on a type of optical systemused, the ophthalmologist has a given field of view of the fundus, whichmay vary from a narrow field of view to a wide field of view that canextend to peripheral regions of the fundus. For many types ofvitreoretinal surgery using the surgical microscope, the surgeon maydesire to have a very wide field of view of the fundus that extendsbeyond the equator and even out to the ora serrata. The optical systemto provide the view of the fundus to the surgeon during vitreoretinalsurgery may include a special ocular lens, of which three types aretypically used: a direct (piano, flat, or magnifying) contact lens, anindirect non-contact lens, or an indirect contact lens.

A contact lens is in physical contact with the cornea and therefore hasa concave surface to match the convex surface of the cornea. Typically asmall amount of refractive index-matching gel or fluid resides betweenthe cornea and the contact lens to prevent unwanted extraneousinterfacial reflections and to protect the cornea from dehydration.

A non-contact lens does not touch the eye and is spaced a certainworking distance away from the eye.

A direct lens creates a non-inverted virtual image of the fundus behindthe eye lens and generally in front of the fundus. The surgeon uses thesurgical microscope to focus directly on this non-inverted virtualimage, which is also referred to as an intermediate image plane or afocus plane. The direct lens enables the surgeon to directly view thefundus.

An indirect lens creates an inverted real image in the intermediateimage plane in front of the eye lens (between the eye lens and thesurgical microscope) and the surgeon uses the surgical microscope tofocus on this intermediate image plane. The indirect lens enables thesurgeon to indirectly view the fundus via the intermediate image plane.Since the indirect lens image is inverted to the viewer looking throughthe surgical microscope, typically an inverter lens is added to thesurgical microscope to re-invert the fundus image to match the physicalorientation of the eye during vitreoretinal surgery.

A direct contact lens can be placed onto the eye and is generally thinenough axially to normally remain in place on the cornea duringvitreoretinal surgery. In certain optical systems, direct contact lenseshave self-stabilizing features on the lens, such as base extensions thatassist in keeping the direct contact lens from moving during surgery.However, a direct contact lens may not provide a very wide field of viewinto the fundus and of the retina and the field of view may be limitedto about 30 degrees.

An indirect non-contact lens is not in contact with the eye and may befixed to the surgical microscope. Therefore, the indirect non-contactlens may avoid issues of positional instability and additional resourcesinvolved (such as having a skilled surgical assistant to hold orreposition the lens) during vitreoretinal surgery. At least for thesereasons, the indirect non-contact lens may be the ophthalmic surgicallens often chosen by many ophthalmologists. However, an indirectnon-contact lens may be limited in the field of view of the fundusprovided to the surgeon during vitreoretinal surgery. For example, thefield of view using an indirect non-contact lens may be limited to lessthan about 140 degrees (full angle) and may be about 10 degrees lessthan wide angle contact lenses.

In order to see beyond the region of fundus viewable at one time withthe indirect non-contact lenses, the surgeon may employ varioustechniques during vitreoretinal surgery. For example, the surgeon mayindent a peripheral region of sclera to push the fundus in the affectedregion into the field of view. The surgeon may rotate the eye off theoptical axis to direct the field of view onto the desired peripheralregion. In some instances, a combination of techniques is used.Frequently rotating the eye or depressing the sclera to view peripheralregions of the fundus are extraneous operations during vitreoretinalsurgery that are performed for the purpose of obtaining a sufficientview and do not contribute to the primary treatment purpose of thesurgery. Such extraneous operations may result in additional trauma forthe patient, increased time of surgery, and increased likelihood ofsurgical complications and may be undesirable for at least thesereasons.

An indirect contact lens may provide a much greater field of view of thefundus than other types of ophthalmic surgical lenses. Indirect contactlenses may provide a field of view up to about 170 degrees (full angle),essentially out to the very edge of the retina at the ora serrata in asingle image. However, indirect contact lenses, which rest on the corneaduring vitreoretinal surgery, are generally top-heavy due to theiroptical construction and typically move in angular and positionalorientation after initial placement on the eye. Indirect contact lensesmay also be relatively sensitive to small movements by the patientduring surgery, which is undesirable. Therefore, the surgeon oftentimesengages the help of an assistant, either to continually hold theindirect contact lens in place or to frequently reposition the indirectcontact lens many times during the course of vitreoretinal surgery.Despite the large field of view afforded, the lack of positionalstability and the additional involvement of a skilled surgical assistantto position the lens may be undesirable. At least for these reasons, thefree-standing indirect contact lens may be an unpopular choice amongvitreoretinal surgeons.

SUMMARY

The disclosed embodiments of the present disclosure provide forilluminating and viewing the extreme periphery of the fundus duringvitreoretinal surgery without implementing extraneous operations,without using additional skilled surgical personnel, and without havingthe positional instability of a free-standing indirect contact lens.

In one aspect, a disclosed method for performing ophthalmic surgeryincludes positioning a first optical axis of a surgical microscope alonga second optical axis of an eye of a patient, and viewing an interiorportion of the eye using an indirect contact lens in contact with theeye. The indirect contact lens may be mechanically coupled to thesurgical microscope.

In any of the disclosed embodiments, the indirect contact lens may bemechanically coupled to the surgical microscope to prevent tilting ofthe indirect contact lens away from the first optical axis.

In any of the disclosed embodiments, the method may further includemanually lowering the indirect contact lens to be in contact with theeye. When the indirect contact lens is in contact with the eye, themethod may include focusing the surgical microscope at a focus plane ofthe indirect contact lens.

In any of the disclosed embodiments, the indirect contact lens may bemechanically coupled to the surgical microscope to enable movement ofthe indirect contact lens with respect to the surgical microscope in adirection corresponding to the first optical axis.

In any of the disclosed embodiments, the method may further includemechanically coupling the indirect contact lens to the surgicalmicroscope using a surgical microscope attachment. In the method, theindirect contact lens may be mechanically coupled to the surgicalmicroscope to enable rotation about a mounting member of the surgicalmicroscope attachment. In the method, the indirect contact lens may bemechanically coupled to the surgical microscope to enable horizontaltranslation with respect to the mounting member. In the method, themounting member may enable movement of the indirect contact lens withrespect to the surgical microscope in a direction corresponding to thefirst optical axis.

In another aspect, a surgical microscope attachment may include amounting member for mounting the surgical microscope attachment to asurgical microscope having an optical axis. The surgical microscopeattachment may include an extension member coupled to the mountingmember. In the surgical microscope attachment, the extension member maytranslate with respect to the mounting member in a first directionaligned with the optical axis. The surgical microscope attachment mayinclude a lens holder coupled to the extension member to position anindirect contact lens for viewing an eye of a patient during ophthalmicsurgery using the surgical microscope. In the surgical microscopeattachment, the lens holder may rotate with respect to the extensionmember and may translate with respect to the extension member in asecond direction perpendicular to the optical axis.

In any of the disclosed embodiments, the surgical microscope attachmentmay include a first bearing coupling the mounting member to theextension member, the first bearing for reducing friction when theextension member translates in the first direction.

In any of the disclosed embodiments, the surgical microscope attachmentmay include a second bearing coupling the extension member to the lensholder, the second bearing for reducing friction when the lens holderrotates about the extension member.

In any of the disclosed embodiments, the surgical microscope attachmentmay include a third bearing coupling the extension member to the lensholder, the third bearing for reducing friction when the lens holdertranslates with respect to the extension member in the second direction.

In any of the disclosed embodiments, the lens holder may further includea coupling member that includes the second bearing and the thirdbearing, an arm member that runs linearly in the third bearing at afirst end and that couples to the indirect contact lens at a second end,and a retaining mechanism at the second end of the arm member to attachthe indirect contact lens to the lens holder.

In any of the disclosed embodiments, the surgical microscope attachmentmay include a detention mechanism to prevent the extension member fromuncoupling from the mounting member. In the surgical microscopeattachment, the detention mechanism may detain the extension member at amaximum translation in the first direction with respect to the mountingmember. In the surgical microscope attachment, a range of translation inthe first direction of the extension member may enable an objective ofthe surgical microscope to focus at a focal plane of the indirectcontact lens.

In any of the disclosed embodiments of the surgical microscopeattachment, the mounting member and the extension member may becylindrically shaped and may be arranged concentrically to each other ata center line. In the surgical microscope attachment, the lens holdermay rotate about the center line. In the surgical microscope attachment,the lens holder may prevent tilting of the indirect contact lens awayfrom the optical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a lateral view of selected elements of an embodiment of asurgical microscope attachment for supporting an indirect contact lens;

FIG. 2 is a depiction of an embodiment of a vitreoretinal surgery usinga surgical microscope and a surgical microscope attachment forsupporting an indirect contact lens; and

FIG. 3 is a flow chart of selected elements of a method for performingvitreoretinal surgery.

DESCRIPTION OF PARTICULAR EMBODIMENT(S)

In the following description, details are set forth by way of example tofacilitate discussion of the disclosed subject matter. It should beapparent to a person of ordinary skill in the field, however, that thedisclosed embodiments are exemplary and not exhaustive of all possibleembodiments.

As used herein, a hyphenated form of a reference numeral refers to aspecific instance of an element and the un-hyphenated form of thereference numeral refers to the collective element. Thus, for example,device ‘12-1’ refers to an instance of a device class, which may bereferred to collectively as devices ‘12’ and any one of which may bereferred to generically as a device ‘12’.

As noted above, free-standing indirect contact lenses, though theyprovide a much greater field of view of the fundus than other types ofophthalmic surgical lenses, are not frequently used by surgeons duringvitreoretinal surgery. Because indirect contact lenses are top heavy inconstruction, such lenses may exhibit positional instability whenresting on the cornea of a patient during surgery. Indirect contactlenses may easily lose angular and positional orientation after initialplacement on the eye, resulting in repeated or continuous manual effortfor repositioning during surgery. Furthermore, the instability of atypical indirect contact lens may be unpredictable during surgery, whichis also undesirable.

As will be described in further detail, the inventors of the presentdisclosure have developed a surgical microscope attachment formechanically supporting an indirect contact lens by a surgicalmicroscope used during ophthalmic surgery. The surgical microscopeattachment disclosed herein may force the indirect contact lens toremain upright, and hence remain aligned with an optical axis of the eyeof the patient, during surgery. The surgical microscope attachmentdisclosed herein may further enable the indirect contact lens to movewithout substantial mechanical resistance in the horizontal and verticaldirection (within certain limits) to conform to the position of the eyeduring surgery. In this manner, the surgical microscope attachmentdisclosed herein may provide positional stability for the indirectcontact lens, while retaining a certain amount of flexibility inmovement, such as from small movements of the patient during surgery.Accordingly, the surgical microscope attachment disclosed herein mayenable the ophthalmic surgeon to enjoy the wide angle viewingcapabilities afforded by indirect contact lenses, without the positionalinstability problems of a free-standing indirect contact lens withoutmechanical support, such as using additional skilled surgical personnel,and without implementing extraneous operations during surgery, such asrotating the eye or indenting the sclera to view desired portions of thefundus.

Referring now to the drawings, FIG. 1 illustrates a lateral view ofselected elements of an embodiment of a surgical microscope attachment100 for supporting an indirect contact lens. FIG. 1 is a lateral viewwith partial cross-sectional views and is a schematic drawing that isnot drawn to scale. As will be described in further detail, FIG. 1 showssurgical microscope attachment 100 fixed to an indirect contact lens 120that rests on an eye 130. Surgical microscope attachment 100, as shown,is comprised of a mounting member 102, an extension member 104, and alens holder 114. As shown, lens holder 114 includes a coupling member114-1, an arm member 114-2, and a retaining mechanism 114-3. In variousembodiments, surgical microscope attachment 100 may be implemented withfewer or more components than illustrated in the exemplary embodiment ofFIG. 1, which is shown for descriptive purposes.

In FIG. 1, surgical microscope attachment 100 includes mounting member102 for mounting to a surgical microscope (see FIG. 2). Mounting member102 may be any of a variety of structural members used for mechanicalattachment, such a tube, rod, beam, channel, or other type of structuralmember. As shown, mounting member 102 is a hollow cylindrical (or tube)member having center line 103. Although a mounting point of mountingmember 102 to the surgical microscope is omitted from view in FIG. 1 forclarity, it will be understood that surgical microscope attachment 100may be mounted to the surgical microscope to enable an objective of thesurgical microscope to view an indirect image generated by indirectcontact lens 120, and to focus on a focal plane 142 where the indirectimage is generated.

As shown, mounting member 102 is concentrically coupled to extensionmember 104 about center line 103, where extension member 104 is alsoshown as a hollow cylindrical (or tube) member. When mounting member 102has another shape, such as a hollow square or rectangular cross-section,for example, extension member 104 may be correspondingly shaped to mateor couple with mounting member 102. Extension member 104 is able totranslate vertically in direction 108 with respect to mounting member102.

As shown in FIG. 1, extension member 104 is telescopically coupled tomounting member 102 about center line 103. Between extension member 104and mounting member 102, bearings 106 may enable extension member 104 torun in direction 108 with very low friction. Additionally, a detentionmechanism may prevent extension member 104 from dropping out of mountingmember 102. Specifically, extension member 104 may have a flange 104-1that abuts on ring 102-1 of mounting member 102 to prevent extensionmember 104 from falling out. Other detention mechanisms may be used indifferent embodiments. In this manner, extension member 104 may bedetained at a maximum vertical translation with respect to mountingmember 102, but may travel freely in direction 108 at other positionswith very low friction.

In FIG. 1, lens holder 114 is mounted to the other end of extensionmember 104. Lens holder 114 may be rotatably coupled to extension member104 at coupling member 114-1 by means of bearing 118. Coupling member114-1 may be fixed to extension member 104 to prevent any movement,other than the rotation enabled by bearing 118, therebetween. Bearing118 may enable rotation with very low friction about center line 103,shown by rotational direction 112. In various embodiments, bearing 118may enable full 360 degrees of rotation without limit. As couplingmember 114-1 rotates using bearing 118, lens holder 114, including armmember 114-2 and retaining mechanism 114-3, rotates correspondingly. Atsmall angles of rotation enabled by bearing 118, indirect contact lens120, when mounted to surgical microscope attachment 100, may be enabledto move horizontally in a direction perpendicular to the page of FIG. 1.

In FIG. 1, coupling member 114-1 further includes bearing 116 thatprovides linear movement of arm member 114-2 with very low friction. Asshown, the linear movement of arm member 114-2 enabled by bearing 116 isin direction 110 that is parallel to the page of FIG. 1. More generally,arm member 114-2 is enabled to translate radially with respect to centerline 103. Arm member 114-2 may be detained within coupling member 114-1at one end using any of a variety of detention mechanisms (not shown).In some embodiments, one end of arm member 114-2 may be freely removedfrom, or inserted into, coupling member 114-1 without a detentionmechanism. When mounted to surgical microscope attachment 100, armmember 114-2 may enable indirect contact lens 120 to move horizontallyin the radial direction with respect to center line 103. At another endof arm member 114-2, retaining mechanism 114-3 enables attachment ofindirect contact lens 120 to surgical microscope attachment 100, andaccordingly, to the surgical microscope. As shown, retaining mechanism114-3 may be a ring clip that encompasses indirect contact lens 120 andis fixed to indirect contact lens 120. In other embodiments, retainingmechanism 114-3 may be a different type of mechanical couplingmechanism, such as a threaded rod or hole, a clip, an insert, etc., forcoupling indirect contact lens 120 in a fixed manner to arm member114-2. It is noted that different types of retaining mechanism 114-3, toenable use of different types of indirect contact lens 120, includingcommercially available indirect contact lenses, may be included withsurgical microscope attachment 100.

Thus as shown in FIG. 1, indirect contact lens 120 is mechanicallycoupled to the surgical microscope using surgical microscope attachment100 but is still afforded a certain degree of horizontal and verticalmotion with very low friction. Surgical microscope attachment 100 may beused to safely place indirect contact lens 120 on eye 130 duringvitreoretinal surgery and hold indirect contact lens 120 in alignmentwith an optical axis of the surgical microscope (see also FIG. 2), whichmay be aligned with optical axis 131 of eye 130. Even when optical axis131 deviates slightly from the optical axis of the surgical microscopeduring vitreoretinal surgery, surgical microscope attachment 100 maystill enable useful imaging of the fundus by keeping indirect contactlens 120 aligned with the optical axis of the surgical microscope. Inother words, even when optical axis 131 of the eye tilts away from theoptical axis of the surgical microscope during vitreoretinal surgery,surgical microscope attachment 100 may enable the surgeon to continueviewing the fundus with a wide angle view using indirect contact lens120. Furthermore, surgical microscope attachment 100 may enable thesurgeon to continue viewing the fundus without significant risk ofinjury to the patient that might otherwise result from an opticalarrangement that is fixed and does not afford any motion of an ocularlens.

Specifically, indirect contact lens 120 may include a concave portion137 that mates with the convex shape of cornea 138 where opticalcoupling agent 139 is used. Optical coupling agent 139 may be applied asa film interfacial layer to prevent unwanted reflections and to enableviewing into eye 130 along optical axis 131. The indirect imagegenerated by indirect contact lens 120 at focal plane 142 may correspondto a field of view 140 that is relatively wide and may extend out beyondeye equator 133 to the ora serrata 136 where retina 134 ends. Thus,field of view 140 includes a large portion of the fundus that is filledwith vitreous humor 132, including all or most of retina 134. In thismanner, the surgeon is afforded a safe and stable view to perform any ofa variety of surgical techniques on eye 130. Furthermore, surgicalmicroscope attachment 100 may enable relatively quick removal andreplacement of indirect contact lens 120 on eye 130, even duringsurgery, as desired.

Modifications, additions, or omissions may be made to surgicalmicroscope attachment 100 without departing from the scope of thedisclosure. The components and elements of surgical microscopeattachment 100, as described herein, may be integrated or separatedaccording to particular applications. Surgical microscope attachment 100may be implemented using more, fewer, or different components in someembodiments.

Turning now to FIG. 2, a depiction of an embodiment of a vitreoretinalsurgery 200 using a surgical microscope 202 and surgical microscopeattachment 100 for supporting indirect contact lens 120 is shown. InFIG. 2, the use of surgical microscope attachment 100 as shown in FIG. 1with a patent and a surgeon is depicted. Although FIG. 2 is shown withsurgical microscope 202 above the patient, it is noted that differentorientations of the patient with respect to surgical microscope 202 maybe practiced in different embodiments.

The patient has an eye exposed using speculum 204 that is in contactwith indirect contact lens 120, while the surgeon is viewing the fundusof the patient's eye using surgical microscope 202. As a result ofbearings 106, 118, and 116, explained above with respect of FIG. 1,which provide low friction movement, very little vertical or horizontalpressure is extorted on the eye of the patient in vitreoretinal surgery200. Because indirect contact lens 120 still rests freely on the cornea,indirect contact lens 120 may be self-retaining due to the weight ofindirect contact lens 120 transmitted to convex portion 137, whichresists lateral sliding of indirect contact lens 120 relative to thecornea. Therefore, when the patient's eye moves slightly relative tosurgical microscope 202, indirect contact lens 120 stays with thepatient's eye and may move relative to surgical microscope 202. However,as explained previously, surgical microscope attachment 100 maintainsalignment of indirect contact lens 120 with an optical axis 206 ofsurgical microscope 202, thereby enabling useful imaging for the surgeonto be maintained during surgery without external intervention, such asby a skilled surgical technician.

When indirect contact lens 120 is initially placed on the eye, opticalaxis 131 of the eye will generally be aligned with optical axis 206 ofsurgical microscope 202. However, when the patient makes a smallmovement during surgery, such as a lateral or vertical movement of thehead, optical axis 131 may become slightly non-aligned with optical axis206. Even when optical axis 206 is no longer perfectly aligned withoptical axis 131, surgical microscope attachment 100 may keep indirectcontact lens 120 aligned with optical axis 206 to enable useful viewingof the fundus during surgery without interruption. In this manner usingsurgical microscope attachment 100, as disclosed herein, extraneousoperations to view peripheral regions of the fundus may be avoided, andadditional personnel or manual actions to maintain the positionalstability of indirect contact lens 120 may be eliminated.

The objective used with surgical microscope 202 may have a focal lengthof about 175 mm to 225 mm that focuses on focal plane 142 of indirectcontact lens 120. It is noted that surgical microscope 202 may provideillumination for the fundus that is projected through indirect contactlens 120. Thus the surgeon may be provided with field of view 140 (seeFIG. 1) via surgical microscope 202 and may safely proceed with any of avariety of vitreoretinal surgical procedures (not shown).

Referring now to FIG. 3, a flow chart of selected elements of anembodiment of a method 300 for performing vitreoretinal surgery, asdescribed herein, is depicted in flowchart form. Method 300 describessteps and procedures for using surgical microscope attachment 100 withindirect contact lens 120 (see FIGS. 1 and 2) to view the fundus of aneye and to enable further surgical procedures based on the view of thefundus. It is noted that certain operations described in method 300 maybe optional or may be rearranged in different embodiments. Method 300may be performed by a surgeon or by other medical personnel. In someembodiments, at least certain portions of method 300 may be automated,for example using servo-mechanical control associated with certainaspects of the surgical microscope, such as raising or lowering thesurgical microscope.

Method 300 may begin, at step 302, by positioning a surgical microscopelaterally along an optical axis of an eye of a patient and verticallyabove the eye, the surgical microscope having a surgical microscopeattachment mounted thereon to hold an indirect contact lens. In certainembodiments of step 302, the patient is moved relative to the surgicalmicroscope. Then, at step 304, the indirect contact lens is fixed to aretaining mechanism of a lens holder included with the surgicalmicroscope attachment. At step 306, the indirect contact lens is heldmanually and is raised away from the eye such that an extension memberof the surgical microscope attachment translates vertically with respectto a mounting member of the surgical microscope attachment. Whileholding the indirect contact lens above the eye, at step 308, thesurgical microscope is vertically lowered towards the eye to a verticalposition within a vertical translation range of the extension memberroughly corresponding to a focal plane of the indirect contact lens whenplaced on the eye. At step 310, the indirect contact lens is manuallylowered to be in contact with the eye. An optical coupling agent may beapplied at step 310 (or prior to step 310) between the indirect contactlens and the cornea of the eye. At step 312, the surgical microscope isfocused at the focal plane of the indirect contact lens. After step 312,the surgeon may view the fundus of the eye using the indirect contactlens and proceed with any of a variety of surgical procedures.

As disclosed herein, an indirect contact lens is mechanically coupled toa surgical microscope during ophthalmic surgery, such as vitreoretinalsurgery. The indirect contact lens rests on a cornea of an eye of apatient during the surgery but is supported by a surgical microscopeattachment having multiple degrees of freedom to accommodate smallmovements of the eye while remaining aligned to an optical axis of thesurgical microscope.

The above disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments which fall within thetrue spirit and scope of the present disclosure. Thus, to the maximumextent allowed by law, the scope of the present disclosure is to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

What is claimed is:
 1. A surgical microscope attachment, comprising: acylindrical mounting portion attached to a surgical microscope having anoptical axis; a cylindrical extension portion concentrically oriented tothe cylindrical mounting portion, wherein the cylindrical extensionportion is configured to translate with respect to the cylindricalmounting portion in a first direction parallel to the optical axis andin a third direction opposite to the first direction; a lens holderattached to the cylindrical extension portion, the lens holderconfigured to position an indirect contact lens for viewing an eye of apatient, wherein the lens holder rotates with respect to the cylindricalextension portion and the lens holder translates with respect to thecylindrical extension portion in a second direction perpendicular to theoptical axis and in a fourth direction opposite to the second direction;and a first bearing disposed between the cylindrical mounting portionand the cylindrical extension portion, the first bearing configured toassist the cylindrical extension portion to translate in the firstdirection and in the third direction, wherein the cylindrical extensionportion is configured to translate freely with respect to thecylindrical mounting portion in the first direction and the thirddirection, and wherein the cylindrical extension portion, the lensholder, and the indirect contact lens are configured to be freelysupported by the eye when the indirect contact lens is in contact withthe eye.
 2. The surgical microscope attachment of claim 1, furthercomprising: a second bearing disposed between the cylindrical extensionportion and the lens holder, the second bearing assisting the lensholder to rotate about the cylindrical extension portion.
 3. Thesurgical microscope attachment of claim 2, further comprising: a thirdbearing disposed between the cylindrical extension portion and the lensholder, the third bearing enabling the lens holder to translate withrespect to the cylindrical extension portion in the second direction andthe fourth direction.
 4. The surgical microscope attachment of claim 3,wherein the lens holder further comprises: a coupling portion thatincludes the second bearing and the third bearing; an arm that runslinearly in the third bearing at a first end and that couples to theindirect contact lens at a second end; and a retaining band at thesecond end of the arm to fix the indirect contact lens to the lensholder.
 5. The surgical microscope attachment of claim 1, furthercomprising: a flange at one end of the cylindrical extension portion toprevent the cylindrical extension portion from uncoupling from thecylindrical mounting portion, wherein the flange detains the cylindricalextension portion at a maximum translation in the first direction withrespect to the cylindrical mounting portion.
 6. The surgical microscopeattachment of claim 5, wherein a range of translation in the firstdirection of the cylindrical extension portion enables an objective ofthe surgical microscope to focus at a focal plane of the indirectcontact lens.
 7. The surgical microscope attachment of claim 1, whereinthe lens holder rotates about a center line of the cylindrical extensionportion.
 8. The surgical microscope attachment of claim 1, wherein thelens holder secures the indirect contact lens such that a second opticalaxis of the indirect contact lens is parallel to the optical axis of thesurgical microscope.
 9. The surgical microscope attachment of claim 1,wherein the cylindrical extension portion concentrically oriented to thecylindrical mounting portion further comprises: the cylindricalextension portion concentrically oriented to the cylindrical mountingportion within a hollow interior of the cylindrical mounting portion.